9. Patients who are on epoetin alfa or darbepoetin prior to enrollment will be allowed to enroll if they have failed such therapy, failure defined as transfusion requiring despite >/= 6 weeks of epoetin alfa at dose of 40,000 units/week and darbepoetin alfa at dose of 150 mcg/ 2 week. No washout period will be necessary. Upon study entry patients receiving epoetin alfa will be switched over to darbepoetin.